The linker uses four startup files:
•32-bit PA is /opt/langtools/lib/crt0.o
•64-bit PA is /opt/langtools/lib/pa_64/crt0.o
The linker uses this startup file when it is in compatibility mode (+compat) or it is in default standard mode (+std) with the -nosharedoption.
•32-bit IPF is /opt/langtools/lib/hpux32/crt0.o
The linker uses this startup file when it is in default standard mode (+std) with the -nosharedoption.
•64-bit IPF is /opt/langtools/lib/hpux64/crt0.o
The linker uses this startup file when it is in default standard mode (+std) with the -nosharedoption.
If the -pprofiling option is specified on the compile line, the compilers link with -L /usr/ccs/lib/libp-lprof. If the-Gprofiling option is specified, the compilers link with /usr/ccs/lib/lip -lgprof.
PA-RISC ONLY:
If the linker option -Iis specified to create an executable file with profile-based optimization, in 32-bit mode icrt0.o is used, and in 64-bit mode the linker inserts /usr/ccs/lib/pa20_64/fdp_init.o. If the linker options -Iand -b are specified to create a shared library with profile-based optimization, in 32-bit mode scrt0.o is used, and in 64-bit mode, the linker inserts /usr/ccs/lib/pa20_64/fdp_init-sl.o. In 64-bit mode, the linker uses the single 64-bit crt0.o to support these options.
For details on startup files, see crt0(3).
The Program's Entry Point
For archive-bound (using the -completecompiler option or the -nosharedlinker option) executables, the entry point is the location at which execution begins in the a.out file. The entry point is defined by the symbol $START$ in crt0.o. In share-bound executables, the entry point is defined by the symbol $START$ in the dynamic loader (dld.so).
The a.out File
The information contained in the resulting a.out file depends on which architecture the file was created on and what options were used to link the program. In any case, an executable a.out file contains information that HP-UX needs when loading and running the file. For example: Is it a shared executable? Does it reference shared libraries? Is it demand-loadable? Where do the text (code), data, and bss (uninitialized data) segments reside in the file? For details on the format of this file, see a.out(4).
Magic Numbers (PA-RISC ONLY)
In 32-bit mode, the linker records a magic number with each executable program that determines how the program should be loaded. There are three possible values for an executable file's magic number:
SHARE_MAGIC | The program's text (code) can be shared by processes; its data cannot be |
| shared. The first process to run the program loads the entire program into virtual |
| memory. If the program is already loaded by another process, then a process |
| shares the program text with the other process. |
DEMAND_MAGIC | As with SHARE_MAGIC the program's text is shareable but its data is not. |
| However, the program's text is loaded only as needed - that is, only as the |
| pages are accessed. This improves process startup time since the entire |